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Unread 08-23-2007, 07:30 AM   #1
jfwireless
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YJ Dual Diaphragm Brake Power Booster

Does anybody know what years the YJ had the dual diaphragm non abs power booster?? I believe it was 1991-1995, the previous years had only a single diaphragm power booster, no better than my current CJ power booster.

I also believe the master cylinder is different, I currently have a 1981 Corvette MC, very large piston and a great bolt on upgrade to my stock CJ power booster. Does anybody know if the 1981 Corvette MC will bolt on to the YJ non abs dual diaphragm power booster?

I see lots of articles on on installing the YJ power booster in the CJ, but nobody talks about the two different YJ power boosters. You need the dual diaphragm version to make a real difference.

The other option of using a GM dual diaphragm booster seems to take some mounting and linkage modifications.

Thanks for any input

Jim

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Unread 08-23-2007, 11:21 AM   #2
diamatron
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goto partsamerica.com and look up brake boosters for the scramblers. I forget what year it was but I ordered the dual diaphram booster loaded and my brakes went from needing two feet to stop to just as good as my 1996 rangers brakes.
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Unread 08-23-2007, 01:09 PM   #3
jayhawkclint
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If you're going to put in the YJ booster, you might want to try out the E350 master cylinder. O'Reilly's part #10-2008.
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Unread 08-23-2007, 01:52 PM   #4
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To my knowledge it was only the 95 YJ's that had the dual diaphragm booster.
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Unread 08-23-2007, 03:31 PM   #5
jfwireless
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Quote:
Originally Posted by jeepwhore
To my knowledge it was only the 95 YJ's that had the dual diaphragm booster.
OK, that most likey is correct, I also believe it takes a different MC, so the E350 MC will not fit the dual diaphragm 1995 YJ booster.

As I recall the YJ single diaphragm booster was good for 1000 lbs of pressure, the YJ dual was good for 1600 lbs of pressure, making it the best choice.

Jim
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Unread 08-23-2007, 04:20 PM   #6
jayhawkclint
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Quote:
Originally Posted by jfwireless
I also believe it takes a different MC, so the E350 MC will not fit the dual diaphragm 1995 YJ booster.
I wasn't necessarily saying use it with the dual diaphragm unit, just use it with any old XJ/YJ booster in general. Here's a link to a similar swap. You have to drill out the mounting holes to 9/16", not really a biggie. Might just work. Had a guy in my local Jeep club do this and raved about the gains. I've got a stock XJ unit in my JEEP with stock MC, and I feel very comfortable in traffic and trails. I brake with my toes now.

http://www.akextreme4x4.com/tech/bra...r_cylinder.htm
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Unread 08-23-2007, 04:38 PM   #7
cromd
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Quote:
Originally Posted by diamatron
goto partsamerica.com and look up brake boosters for the scramblers. I forget what year it was but I ordered the dual diaphram booster loaded and my brakes went from needing two feet to stop to just as good as my 1996 rangers brakes.

It appears that the 1981 is different than the 1982 through 1985 scrambler booster. How can you tell it is a dual diaphram?
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Unread 08-23-2007, 04:38 PM   #8
cromd
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Quote:
Originally Posted by diamatron
goto partsamerica.com and look up brake boosters for the scramblers. I forget what year it was but I ordered the dual diaphram booster loaded and my brakes went from needing two feet to stop to just as good as my 1996 rangers brakes.

It appears that the 1981 is different than the 1982 through 1985 scrambler booster. How can you tell it is a dual diaphram?
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Unread 08-23-2007, 07:20 PM   #9
jfwireless
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OK, found a thread with Van from Vanco giving information on identifying single or dual diaphragm YJ power boosters if they do indeed exist, measure the length of the power booster from the mounting surfaces, where the MC connects and where the booster connects to the mounting brackets.

Single boosters 4 inches long
Dual Boosters 6.25 inches long

After reading the thread I still am not sure if in 1995 Jeep provide some of the dual boosters in any of the YJ's, but I think they did in the Sahara and SE, but not in the Rio Grande.

This is a good thead to read, the information on the YJ power boosters is at the bottom of the thread. This thread is about hydroboost but full of good information. Now I just need to understand if there is a difference in these power boosters with or without ABS and is there really is a dual diaphragm YJ power booster.

http://www.jeepsunlimited.com/forums.../t-568638.html

Jim
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Unread 08-23-2007, 08:13 PM   #10
biozombie
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Check it out, dual vs single. From what I gather the dual was on *some* 94-95 YJ's. Dual has a plastic MC also. I tried to fit a dual on my 4.2l with a mc2100 carb and there was not enough clearance, beware!

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Unread 08-23-2007, 10:51 PM   #11
diamatron
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Quote:
Originally Posted by cromd
It appears that the 1981 is different than the 1982 through 1985 scrambler booster. How can you tell it is a dual diaphram?
Looks like they dont carry it anymore. But.... Napaonline.com does still list it for the 1983 Scrambler. Its alittle pricier then I remember paying, but its a direct replacement without any issues on my 304. Good luck.
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Unread 08-24-2007, 06:13 AM   #12
jfwireless
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Quote:
Originally Posted by biozombie
Check it out, dual vs single. From what I gather the dual was on *some* 94-95 YJ's. Dual has a plastic MC also. I tried to fit a dual on my 4.2l with a mc2100 carb and there was not enough clearance, beware!

Thanks, great picture, that clears up lots. Did the mounting bracket come with the dual booster or did you fabricate that?? The TJ dual booster seems to mount directly to the firewall.

Do you still have the dual booster in the picture?? I would be interested if you want to sell it?

Jim
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Unread 08-24-2007, 10:47 AM   #13
biozombie
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That firewall bracket is stock, and sorry but I already sold it a few months ago. It was a nice booster. My XJ also has what looks like a dual booster, but its also mounted directly to the firewall.
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Unread 08-24-2007, 11:02 AM   #14
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Has anyone bought from this guy on ebay? link

I decided I would just buy a new parts bolt on either from Vanco or Off Again but I just saw this one too. Its significantly less than the others but I'd rather go with a known entity.
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Unread 08-25-2007, 09:53 AM   #15
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Only 95 YJ's with 6 cylinder motors have a dual diaphragm brake booster. The MC on the dual diaphragm has a plastic resivoir. You can buy a new MC at AutoZone for around $85.
You will want one without the ABS system. Be aware that the threads on the MC for the brake lines are metric thread and that the brake lines will need a bubble flare on them to seat properly against the MC.
It is a night and day difference from the CJ power brakes set up.
Like Biozombie said, if you have the 4.2 in your Jeep you will have clearance issues with a dual diaphragm booster and the carb. If you have the 4.2 I would use a single diaphragm YJ booster. It is still a big improvement over the CJ set up. Here is a link that walks you through the swap and lists the part numbers for the brake line adapters,
http://www.desertcj7.com/yj_brake_booster_upgrade.htm
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